Actually it's not planned to read out the whole logbook via datalayer.
There is the possibility to read out the journald directly but certain permissions are needed and it's not a recommended way.
From v0108 on there is the possibility to read out the highest and/or the list of actual errors and warnings. See node "diagnosis/get/actual/list".
Receiving the logbook from inside the PLC does not exist and is (in our opinion) not planned.
Regarding Node-Red an additional reply will be done here
At the moment it is already possible to use Set own diagnosis messages via the ctrlX DataLayer. See more information in the online documentation. Simply click the "view in document" button to open this topic in the document.
For the PLC there should be also some functions already. I will check that and add a comment here.